Despite the fact that asthma and allergy represent the most common conditions for which pregnant women take prescription medications, there is no systematic approach to evaluating the relative risks and safety of these medications with respect to pregnancy outcomes. Such information is critically needed for prescribers to make meaningful risk benefit assessments of these widely used medications and for patients to feel comfortable that the potential adverse effects associated with the drugs prescribed for them have been adequately studied. To fill this critical gap in clinical knowledge, we propose to demonstrate the feasibility of a comprehensive and ongoing system to assess the relative safety of asthma medications in pregnancy. This specific application will demonstrate the feasibility of using an established cohort pregnancy outcome study design (Organization of Teratology Information Specialists or OTIS), to generate and test hypotheses related to the comparative risk (or safety) for birth defects overall, preterm delivery, small-for-gestational age infants, and perinatal complications associated with recently introduced asthma medications for which there is little to no current data. In addition, this demonstration project will integrate the findings of the cohort study with data derived from a parallel and complementary case-control demonstration application submitted by the Slone Epidemiology Center's Birth Defects Study. Finally, this demonstration project will work in close collaboration with the American Academy of Asthma, Allergy, and Immunology (AAAAI) to develop the infrastructure for an ongoing comparative pregnancy safety system. This will include an expert independent advisory committee to evaluate the accumulating data from the OTIS cohort study as well as case-control data, and to offer recommendations regarding relative risk and safety of asthma medications in pregnancy. These three activities taken together will further demonstrate the feasibility of the system for studying comparative safety of other recently marketed and/or commonly used medications in pregnancy.